Thermally responsive controller and switch assembly therefor

Abstract

A thermostat having a low force output, snap-acting thermally responsive bi-metal disc operative through a pushrod to move the blade of an SPDT switch at a pre-selected temperature. The switch has a cantilever blade formed of a unitary thin metal strip having a flexible stem with a first rigid tongue extending therefrom with a heavy current carrying moveable contact thereon for a normally closed contact set. The pushrod contacts the rigid first tongue for switch actuation. A second flexible tongue extends from the stem and has an integral low current normally open contact thereon for a contact set which is closed upon switch blade actuation. Upon further temperature rise, after switch actuation, pushrod over-travel on the first tongue is absorbed by resilient flexing of the stem and second tongue thereby providing a wiping action to the closed low current contact set.

What is claimed is: 
     
       1. A thermally responsive switch controller assembly comprising: (a) body means having a plurality of spaced electrical terminals mounted thereon and adapted for circuit connection thereto;   (b) first stationary contact means mounted on said body means and connected to one of said terminals;   (c) second stationary contact means disposed on said body means in spaced relationship to said first contact means and connected to another of said terminals;   (d) blade means having a first portion thereof stationary with respect to said body means and a second portion moveable with respect to said first and second stationary contact means, said second portion incuding moveable contact means;   (e) actuator means including thermally responsive means operative in response to experiencing a pre-selected temperature to move said blade means from a position completing a first circuit through said first stationary contact means to a position completing a second circuit through said second stationary contact means in which position said first circuit is broken;   (f) said blade means second portion having a resiliently flexible stem attached to said stationary portion and a substantially rigid first tongue means and resiliently flexible second tongue means extending in cantilever from said stem, said first tongue means including a first moveable contact, said second tongue means including a second moveable contact and said actuator means includes a member operatively contacting said first tongue means, whereupon exposure of said thermal means to said pre-selected temperature said actuator member moves said first tongue means by resilient flexing of said stem portion for effecting breaking of said first circuit and said second tongue is moved to effect completing said second circuit and thereafter upon further temperature increase further movement of said member substantially is absorbed by said resilient flexing and said second tongue means.   
     
     
       2. The switch controller assembly defined in claim 1, wherein said blade means comprises a unitary flat spring member with said first tongue having an elongated configuration with said second tongue having a yoke configuration and disposed about said first tongue. 
     
     
       3. The switch controller assembly defined in claim 1, wherein said blade means comprises a unitary elongated member having said first tongue means disposed within said second tongue means, said first and second tongue means extending in cantilever arrangement from said stem portion of said blade means with said second moveable contact disposed on the free end of said second tongue means and said first moveable contact disposed on the free end of said first tongue means. 
     
     
       4. The switch controller assembly defined in claim 1, wherein said blade means comprises a unitary generally planar member having an elongated configuration with its thickness substantially less than the width thereof, said first and second tongue means each comprise a member cantilevered from said stem portion with said first moveable contact disposed on the free end of said of said first tongue means, and said second moveable contact disposed on the free end of said second tongue means, said first tongue means having an actuation surface formed thereon intermediate with free end thereof and the base thereof, said actuation surface operatively contacting said actuator means. 
     
     
       5. The controller defined in claim 1, wherein said thermally responsive means comprises a bimetal member. 
     
     
       6. The controller assembly defined in claim 1, wherein said thermally responsive means comprises a bimetal member and said actuator means includes a guide means defined by said housing means and said member comprises a pushrod slidably received in said guide means. 
     
     
       7. The controller assembly defined in claim 1, wherein said thermally responsive means comprises a bimetal member and said actuator means includes pushrod means slidably received in said guide means, said pushrod means having one end thereof operatively contacting said bimetal member and the other end thereof operatively contacting said first tongue means. 
     
     
       8. The controller assembly defined in claim 1, wherein said thermally responsive means comprises a snap-acting bi-metal member. 
     
     
       9. A thermally responsive SPDT switch controller assembly comprising: (a) body means having at least three spaced electrical terminals mounted thereon and adapted for circuit connection thereto;   (b) blade means having an end portion mounted on said body means and having a plurality of electrical contact means provided thereon, said blade means being operative, upon actuation, for movement of said contact means with respect to said body means;   (c) thermally responsive means including snap-acting means operable upon experiencing a pre-determined temperature to move said blade means and said contact means;   (d) said blade means comprising a generally thin flat strip of resiliently flexible material having an elongated configuration with one end thereof mounted on said body means and electrically connected to a first one of said electrical terminals, said blade means having a resiliently flexible stem attached to said mounted end and having a first and second spaced tongue means formed integrally therewith and extending in cantilever from said stem portion, said first tongue means configured so as to be substantially rigid and having one of said plurality of electrical contact means disposed thereon and said second tongue means resiliently flexible and having another of said contact means disposed thereon, said first tongue means including means defining an actuation surface in operative contact with said thermally responsive means for movement thereby;   whereupon said thermally responsive means experiencing said pre-determined temperature said stem portion is resiliently flexed and said first tongue means moves to break a normally closed circuit connection with a second of said electrical terminal means and is operative to cause said second tongue means to move with said first tongue means to complete a normally open circuit with a third of said electrical terminal means, said blade means thereafter at increased temperatures absorbing overtravel of said snap acting means by resilient flexing of said stem and said second tongue means.   
     
     
       10. The switch controller assembly defined in claim 9, wherein; (a) said second tongue means extends a greater distance in the direction of elongation of said blade than said first tongue means and is more flexible than said stem;   (b) said blade means has the base of said second tongue means formed longitudinally intermediate said actuation surface and said mounted end portion and said blade means has the width thereof reduced in said stem portion to cause the substantially all of the resilient flexing of said pre-determined temperature to occur in said stem portion.   
     
     
       11. The switch controller assembly defined in claim 9, wherein said first tongue means has a moveable electrical contact mounted thereon adjacent the free end thereof and one of said terminals has a stationary electrical contact thereon and said stationary contact has the first moveable contact in normally closed arrangement therewith. 
     
     
       12. An improved single pole double throw switch assembly comprising: (a) body means having a plurality of electrical terminals received thereon and adapted for external circuit connection thereto;   (b) normally closed electrical contact means electrically connected to a first one of said terminals;   (c) normally open electrical contact means electrically connected to a second one of said electrical terminals;   (d) blade means electrically connected to a third one of said electrical terminals and including moveable contact means, said third terminal operative as a common conductor for said first and second terminals, wherein said blade means comprises an elongated strip of resilient flexible material having a stem portion disposed in cantilever arrangement on said body means and having (i) a first tongue portion extending longitudinally of and cantilevered from said stem portion, said first tongue portion configured to be substantially rigid;   (ii) a second tongue portion cantilevered at its base from said stem portion and extending longitudinally thereof, said second tongue portion being resiliently flexible;   (iii) said first tongue having an actuation surface provided thereon intermediate the free end thereof and the base thereof;     (e) means defining a first moveable contact disposed adjacent the free end of said first tongue;   (f) means defining a second moveable contact disposed adjacent the free end of said second tongue;   (g) plunger means operative upon actuation to contact said actuation surface and effect movement of said blade means, wherein said stem portion is resiliently flexed and said first moveable contact is moved to break a circuit with said normally closed contact and said second tongue portion is moved substantially without flexing to effect making of a circuit between said second moveable contact and said normally open contact, and thereafter, further movement of said actuator means is absorbed by resilient deformation of said stem portion said second tongue means and for effecting wiping between said closed contacts.   
     
     
       13. The switch assembly defined in claim 12, wherein said first and second tongue portions extend longitudinally in spaced generally parallel arrangement. 
     
     
       14. The switch assembly defined in claim 12, wherein said first and second tongue portions extend longitudinally in spaced parallel arrangement and said second tongue comprises a yoke disposed about said first tongue portion. 
     
     
       15. The switch assembly defined in claim 12, wherein said first tongue portion includes stiffening means formed integrally therewith for causing said first tongue to be substantially more resistant to resilient flexing than said second tongue means. 
     
     
       16. The switch assembly defined in claim 12, wherein said actuation surface comprises a curved surface formed by local deformation of said strip. 
     
     
       17. In a single pole double throw switch having a normally closed contact set and a normally open contact set, the improvement comprising: blade means including means defining a moveable one of said normally open and normally closed contact sets, said blade means comprising a unitary elongated strip of resilient material one end thereof fixed and said strip disposed for resilient cantilever deflection about said fixed end, said strip having formed integrally therewith a first longitudinally extending tongue portion and a second logitudinally extending tongue portion, said first tongue configured so as to be rigid and said second tongue resiliently flexible, said first and second tongue portions having the base thereof formed at a generally common longitudinal station of said strip, said first tongue portion defining an actuation surface adopted for contact with a force transmitting actuator, said strip having the stem portion thereof longitudinally intermediate said tongue base wherein, upon said actuation surface experiencing an actuation force, said stem portion is resiliently flexed causing said first tongue to open said normally closed contact set, and said second tongue is moved to effect closing of said normally open contact set, and thereafter further application of said actuation force is substantially absorbed by resilient flexing of said second tongue and said stem portion of said strip.   
     
     
       18. In a single pole double throw switch assembly having a normally closed contact set and a normally open contact set and moveable blade means for effecting breaking of said normally closed set and making of said normally open set, the improvement comprising: said blade means comprising a unitary elongated strip of resiliently flexible material having; (i) one end thereof fixed and a resiliently flexible stem portion extending in cantilever arrangement therefrom,   (ii) a first tongue portion extending in cantilever from said stem portion and having one of said normally closed contact set thereon disposed adjacent or at the free end thereof said first tongue configured so as to be substantially rigid,   (iii) a second tongue portion extending in cantilever from said stem portion and having one of said normally open contact set thereon disposed adjacent or at the free end thereof, said second tongue being configured so as to be resiliently flexible;     wherein, upon application of an actuation force to said first tongue portion, said stem portion flexes resiliently and said first tongue is moved to break said normally closed contact set and said second tongue is moved to close said normally open contact set, and thereafter continued application of said actuation force is absorbed by resilient flexing of said stem and said second tongue, thereby effecting a wiping action of said closed contact set.